The present invention relates to an iron-type golf club head having excellent durability and excellent weight distribution design.
In recent years are proposed iron-type golf club heads which are improved in location of the center of gravity of the heads by joining two or more kinds of members made of different metallic materials. An example of such iron-type golf club heads is shown in FIGS. 16A and 16B. This iron-type golf club head “a” comprises a head body “b” having a recess portion “d”, for example, on a head bottom side, and a weight member “c” which is made of a metallic material having a larger specific gravity than the head body “b” and is fitted to the recess portion “d” of the body “b”. Since a larger amount of weight can be allocated on the head bottom side, such a club head “a” has the advantage that the location of the club head's center of gravity is low and deep. A golf club head of this type is also disclosed in JP-U3089247.
The head body “b” and the weight member “c” are joined together, for example, by welding them in a state that the facing surfaces thereof are brought into substantial contact with each other. The welding is carried out by imparting a molten metal or a heat energy to the interface between the recess portion “d” and the weight member “c” from a head's periphery side.
However, as shown in FIG. 16B in an enlarged form, there may occur a case that the whole interface between the recess portion “d” and the weight member “c” is not completely welded by such a welding applied from the head's periphery. That is to say, a contact face “p” between the recess portion “d” and the weight member “c” may include a welded part “j” and a non-welded part “n” continuing the back of the welded part “j”. In such a case, there is a possibility that the weight member is vibrated through the non-welded part “n” by impact of the head body “b” receiving at the time of hitting a golf ball or at the time of contacting the ground, thus resulting in generation of cracks at the welded part “j”. Particularly, in the case that the recess portion “d” is deeply dented toward the inside of the head, or in the case of plasma or Tig welding that the depth of penetration of weld bead is relatively small, this tendency is noticeable.
In case of autogenous welding such as laser welding or plasma welding, it is desired that the weight member is in close contact with the surface of the recess portion “d” of the head body “b”, in other words, there is no gap at the interface. However, since conventional club heads “a” are designed so that the whole facing surfaces of the recess portion “d” and the weight member “c” come into contact with each other, gaps are easy to generate at the contact surface to be welded due to variation in processing accuracy for the recess portion and the weight member, and may trigger a production of defective goods.
It is an object of the present invention to provide an iron-type golf club head which is improved in degree of freedom of weight distribution design while suppressing generation of cracks in a welded portion between the head body and the weight member over a long term.
This and other objects of the present invention will become apparent from the description hereinafter.